Cross-reference is made to U.S. patent application Ser. No. 11/646,213, filed Dec. 27, 2006, entitled “Lamp Igniter Module and Transformer Carrier”; Ser. No. 11/646,009, filed Dec. 27, 2006, entitled “Lamp Transformer”; Ser. No. 11/645,879, filed Dec. 27, 2006, entitled “Lamp Transformer Assembly”; and Ser. No. 11/513,777, filed Aug. 31, 2006, entitled “Lamp Transformer”.
This disclosure relates to an improved high voltage transformer assembly and method of improving the coupling of the high voltage transformer assembly, and a method for enclosing the high voltage transformer within the burner or igniter enclosure in an automotive headlamp application. It will be appreciated, however, that selected aspects may be used in related environments and applications.
Discharge lamp automotive headlamp designs are generally known in the art. For example, U.S. Pat. No. 7,042,169 discloses a gas discharge lamp base where the transformer includes a bar-core or rod-type transformer. Another automotive headlamp design is disclosed in DE 197 51 548, where the ignition transformer includes an electrically non-conductive, Ni—Zn ferrite core, a gap in the core, and a non-conductive solid body disposed in the gap. The solid body protrudes from the body at one side. Yet another automotive headlamp design is shown and described in U.S. Pat. No. 6,181,081. It describes a starting device that includes a transformer with two primary windings connected in parallel and a secondary winding.
A split core arrangement is desirable since it changes the reluctance of the component and the associated BH curve. Thus, as current or flux increases, greater voltage is obtained. Further, the voltage out of the transformer assembly is related to the input voltage multiplied by a function that is related to the number of turns in the secondary winding, and to the number of primary windings as multiplied by a constant.
It is desirable to know the voltage expected from a transformer assembly so that the manufacturer can rely on the expected operation of the headlamp. The coupling factor is dependent on a number of factors, such as geometry, size, shape, number of turns, material, distance, etc. In automotive headlamp designs, there is a limit to the number of turns that is available. By carefully controlling these various factors, coupling is improved. The dimensional constraints of the housing size are dictated by the automotive industry. Likewise, the positioning of the primary winding is important. The positioning must be predictable so that the desired, predetermined voltage out is obtained. Thus, alternative solutions are needed to more closely control the coupling and provide the high voltage necessary for instant startup of headlamps, i.e., on the order of 25 kV.
It is also desirable to provide a transformer assembly design that is adaptable to different headlamps. The headlamps are often referred to or rated as D1-D5 applications, for example, and require different current levels because of the dose and operational characteristics of the lamp. For example, a D1 headlamp incorporates mercury into the fill, needs less steady state current to operate, and usually permits use of lower gage wire for the turns. A D3 lamp, on the other hand, is mercury free and needs greater current. For example, 0.4 amps may be required for a D1 lamp, while 0.8 amps are required for a D3 lamp. Thus, a need exists to provide a transformer design that allows for a reduction in the number of turns in the secondary winding, and yet increases its current carrying capability so that it is suitable for use in D1-D5 applications.
Moreover, simplified manufacturability of the transformer is also desired as well as reduced variation in the coupling factor to improve the performance of the transformer assembly.